Thread controlling and severing mechanism for sewing machines



M. MCCANN April 11, 1944s 2,346,594 THREAD co1-1TRoLLING AND sEvERING MEcHANIsM FOR SEWING MACHINES 2 Sheets-Sheet l Filed June 23, 1942 April ll, 1944 M, MCQANN 2,346,534

THREAD CONTROLLING AND SEVERING MECHANISM FOR SEWING MACHINES Filed June 23, 1942 2 Sheets-Sheet 2l Patented Apr. 1l, 1944- THREAD CONTROLLING AND SEVERING MECHANISM FOR SEWING MACHINES Y Michael McCann, Ozone Park, N. Y., assignor to The Singer Manufacturing Company, Elizabeth. N. J., a corporation of New Jersey Application June 23, 1942, Serial No. 448,062

Claims.

This invention relates to sewing machines and more particularly to means for breaking the sewing thread at the completion of a sewing operation.

It is old and well known, in tacking and article attaching machines, as shown, for example in U. S. patent to Lyons, No. 1,018,201, Feb. 20, 1912, to break the sewing thread, at the completion of a sewing cycle, by raising the work-clamp and the work supported thereby while the last threadloop is retained by the loop-taker.

This means of severing sewing threads has, however, been ineffective when sewing with thread having a substantial amount of elasticity such, for example, as nylon thread. This is because of the fact that, during upward movement of the work-clamp (which movement is limited), the thread will merely stretch and will not be broken.

The present invention has as its primary object to provide means for taking substantially all of the stretch out of that .portion of the elastic sewing thread adjacent the stitch-forming mechanism so that the thread may be broken by the normal lifting movement of the work-clamp.

A further object of the invention is to provide means cooperating with and actuated by the clamp-lifting mechanism of a sewing machine for rst clamping the thread between the stitch forming mechanism and the source of supply and thereafter taking out of that portion of the thread adjacent the stitch-forming mechanism substantially all of the stretch therein so that normal lifting of the work-clamp will break the thread.

With the above and other objects in view as will hereinafter appear, the invention comprises the devices, combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

In the drawings,

Fig. 1 is a side elevation of a tacking machine embodying the present invention.

Fig. 2 is a vertical sectional view substantially on the line 2-2 of Fig. 1.

Fig. 3 is a fragmentary left end elevation, partly in section, of the machine shown in Fig. 1 showing the work-clamp in operative position.

Fig. 4 is a fragmentary view similar to the lower portion of Fig. 3 but showing the workclamp raised to break the thread.

Fig. 5 is a vertical section substantially on the line 5-5 of Fig. 3 but with the work-clamp and the parts connected therewith raised to the position shown in Fig. 4.

Fig. 6 is a diassembled perspective view of a presser-foot supporting frame and a carrying bracket therefor, later to be described.

Referring more specifically to the drawings, the invention is disclosed as embodied in a tacking machine adapted particularly for tacking bands and bows on mens hats. The machine comprises essentially a base I having a forwardly extending cylindrical work-supporting bed 2 in which is journaled a rotary looper shaft 3 carrying, at its forward end a rotary chainstitch looper 4. Secured upon the base I is a bracket-arm comprising a standard 5, and an overhanging arm 6 which terminates in a head 1 in which is mounted, for vertical reciprocation, a needle-bar 8 carrying, at its lower end, an eyepointed needle 9 which cooperates with the loop- `er 4 in the formation of stitches. A face-plate la is secured to and forms a part of the head l. A main or power shaft In is journaled lengthwise within the arm 6 and carries, at its rear end, loose and tight pulleys II and' I2, respectively. A driving belt (not shown) normally running on the loose pulley, is adapted to be shifted to the tight pulley when it is desired to operate the machine. At its forward end, the shaft I0 is connected, by mechanism not shown, to reciprocate the needle-bar. The looper shaft 3 is driven from the main shaft through the medium of a pair of bevel gears I3 and I4, a vertically disposed shaft I5, journaled in the standard 5, and a second pair of bevel gears I6 and I1 in the base I.

Starting and stopping of the machine is controlled by a conventional stop-motion designated generally as S.

A throat-plate I8 is secured upon the forward end of the bed 2 and is provided with a needlehole I9 through which the eye-pointed end of the needle 9 passes for cooperation with the looper.

Work w to be stitched is carried by a workclamp comprising a clamp base-plate 2D slidingly mounted, for sidewise movements, on the upper surface of the work-supporting bed 2 and actuated through mechanism designated generally as m from a cycle-control cam-wheel 2l mounted on a shaft 22 journaled horizontally in the standard 5 and rotated from the main shaft by a worm 23 and worm-wheel 24, all as is Vcommon in this type of sewing machine. Thework-clamp also includes a work-supporting plate 25 which overlies the throat-plate and which is connected to the forward end of an arm 26 pivoted at 21 to the base of a bracket 28 secured upon the clamp baseplate 20. Cooperating with the plate in holding the Work, is a pair of spaced presser-feet 29 which are pivotally mounted, as by shoulder screws 30, upon a frame 3l which, in turn, is pivotally mounted in a U-shaped bracket 33 by shoulder screws 32. This bracket is secured upon the lower end of a spring-depressed presser-bar 34, mounted for endwise movementin thebracketarm head 1. The presser-feet 2i!V are normally held in the operative position shown in full lines in Fig. 1 and in Fig. 5 by a spring 35 carried by the frame 3|, but the feet maybe swung to the inoperative position, indicated Vin'dotted lines in Fig. 1, to facilitate threading of the needle.

During the tacking operation, the work-supporting plate 25 and the work supported 'thereon are shifted -laterally between successive reciproca ,ticns of the needle, therebyto cause the needie to penetrate the work alternatelyat twoflaterally spaced points. During this lateral shifting of the work, the frame '3l and the A'presser- `feet 2'9 swing back and orth therewith vabout lineages of the 'pivotscrews 32, While hoicmgftne work depressed upon the plate 25. A coilspring surroundingV one of the screws 32 -andjhaving "two 'outwardly'extending'arms ace and as?, of ,vs/'nien the former' engages 'the frame a a while the latter-'engages 'thefup'per edgeof `the bracket 33, normally maintainsthe frame 3| and the presserfee'tfca'rried thereby in one eXtreme ypxjsition but permits them 'to be swung laterally therefrom by the vwork-shifting movement of the work-suplpdrting'plate,25.1 y

The presser-:bar 35 'and 'the presser-feet v c a'rried thereby nay be raised, to permit insertion and removal' "dfthe'work, by jme-'ans ot'a manually ya'c'tufaltlle lever 31 fulcruined'at 35, cna bracket "se 'secured upzm the upper side ofthe overnaiiging anne. The 'forwardend of the lever is Aforked and 'embraces the presser-bar beneath'a collar-fill) secured to the iupp'fer endk of the '-pre'sser bar. vThe opposite "e'ndof the lever'is connected, 4as byf'ac'h'aih fll, to any suitable `lifting treadle Pivtally connected, "byfa 'screw Q2, tothe'lever 31, forwardly ofthefulcrum 35, isthe upperend pria 'two-partlinkirs df'whchnie lower par/M5321 is formed with :a hookpgrncn tra adapted-t9 v en'- gg'e beneath .a bloei; tsfqjustablysecured te an arm t1 prj'ecting upwardly 'from Athe arm 25.

fter 'the machine 'has Lbeen brought to rest at the 'end vf thestit'chingcyc'le the 'lever is swung l'eckwise, as viewed in Fig. 1, ftp lun:l the presser-/feetvher'eupon the 'hook-portion,UtilA of ythe link engages beneath-the bleek te and lifts the work-supporting plate aboutits kpivc t -21 (as indicated in dotted lines in Fi'g jl uthereby breaking the sewing thread, as is weil understood. The iower pan serieuse uni; ne passes vjthrou-gll vthenbifurcated end 28a of "the vbracket 2B and is formed'with 'a cam vportion M whicb, during upwardrnoveinentofuthe `linkengages a studl carried kby bracket, thereby causing-the i-lnkto be shifted iatranytpthe 'pennen 'shown `in dottedy lines in `F"g.'1. VThisvcauzsesthe hook portion 44 to'be disengaged 'from the Vblock 55 whereupon vthe work-supporting plate 25 falls tothe pesition shown in 'full lines in jFig. l, `for the'next operation. A spring 5) surroundingthe 4 pivot screw V52'andhaving'arms 5 1 and'f92 engagfing, respectively, the lever 31 andv the link' 53 holds Athe lowerjend of said link 1 in :ontact with Athe stud T55 'and :constantly tends to mlntain the hook GIB beneath the block 55.

lever '59 and `the bolt head 5111.

The sewing thread t extends from a source of supply through tensions T and T1, thread guides 5D and 5l carried by the head 1 and needle-bar, respectively, thence downwardly and through a thread-check 52, through a thread-eye 53 formed in a plate 54 adjustably mounted` on the face plate 1a, and thence tlfndugh a thread-eye 55 formed in an upstanding arm 3lva constituting a ypart of the frame 3l. From the thread-eye 55 the thread extends to the eye of the needle. The thread-guide 5'l,is carried by the upper end of the needle-bar '-8 and, in conjunction with the stationary Athread-guide 5U, acts as a take-up mechanism yto Aset a stitch upon each upward movement 'of "the needle-bar. This take-up mechanism formsvno part of a thread-stretching device 'hereinafter to be described.

lllntermeoliate the tension Tl and the threadguide 50 there is arranged a thread restraining lmeans or thread-clamp Idesigned to Igrip the "thread at the-"completion 'f fthe sewing `cycle to vprevent thread from being 'drawn from the supply by the thread-breaking operation laterto lbe described. rl'his thread-'clamp 'comprises `a -pair of thread-guides 56, 'secured "by faboltf51 *toa bracket 58 `fixed upon th arm f6. The head 51a 'of the bolt 51 underlies vthe vfthread 't and ffo'rr'ns `a fixed thread-clampingjjaw "Cooperating with the fixed jaw is amovable thread-clamping Tjaw consisting of theforward en'd 59`a of a threadclamping :lever 59 fulcrunedfat '60, 'on :the lbrackv'et 58. The rear-end` of the lever 59 is connected,

vlower end of whichfisfslidiigly ,connected to 'o'ne arm 63EL of a bell-crank lever 63, fulcruined 'at '64 to the'bracket 5B. eollarG-fis-securedupon the rod 62 and a coil spring 56 is interposed 4between the collar andthe arm 63a. The other "arm'63b of the lever 63 carriesa 'round-headed stud 'efr adapted,naar 'nie 'ndjof the stitching cycle, to be engaged by one of 'a plurality of cam plates 68 carriediby thefcarn-wheel 2|. `En- `-53 clockwisafas lseen in, Fig. -2,-`ah'c1 'causingthe threadto vbe gripped 'between the end'aof the y Thus the nachine is brought tofrest, 'atthe'co'mpletion of a sewing cycle, with the thread clamped -by the :thread-clamp and stretched taut `by 1the 'take-up 50, 5|.

To insure that ample 'thread will be provided for making `the -r`s`t 's'titch Iof'the "nex't succeeding cycle, means Y'is iprovided #for pullin'g 1 off a length of Yniveau from fthe risupp1y and :through Athe tensions T 'and T1 Yby the liftingo'f .the workclamp. `",lvhi's 'means comprises fa lever 69, :ful-

crumed, at v1l), to 'the `bracket 58 an'd carrying,

'at its upper end a 'thread-"engaging `wire loop feet and work-clamp the leverSis rocked-counter-clockwise, as seen inFigxZ, causing theIloop 1l to draw thread fromthesupply.

'I'he rea'rend of the1ever`31-lsnormally-maintained elevated by afcoil spring 15,- surrounding a rod 16 connectedto Vthe'lever3`LrearWard1y of its fulcrum 38' and maintained between a bracketfi'l, secured to the bracket 58, and a col- 'lar 18 fixed to the rod 15. A

l' At the end of a 'stitching cycle, the machine comes to rest with the parts in the position shown inFigs. 1 and 3; i. e. with the thread-clamp 51a, 59a closed; with the work-clamp in its lowermost position; with the looper holding the last threadloop; and with the thread taut and inclined downwardly through the thread-eyes 53 and 55. Thereafter the operator actuates a suitable treadle (not shown) thereby turning the lever 31 clockwise, as viewed in Fig. 1. .As hereinbefore stated, this lifts the presser-bar 34 and the presser-feet carried thereby and also lifts the work-clamp from the operative position shown in Fig. 3, and in full lines in Fig. 1, to the position shown in Figs. 4 and 5, and in dotted lines in Fig. 1.

When sewing with cotton or silk thread, which have relatively little elasticity, this upward movement of the work-clamp and the work carried thereby relative to the looper causes the worklimb of the thread-loop held by the looper to be broken adjacent the work. However, when sewing with thread having a substantial amount of elasticity, such for example as nylon thread there is suiicient stretch in the thread that the work-clamp may be raised without breaking the thread, the thread merely stretching.

To overcome this condition and to insure that nylon and similar threads will be broken by the raising of the work-clamp, this invention provides means, operable during the lifting of the work-clamp, for taking out a substantial amount of the stretch in that portion of the thread adjacent the stitch-forming mechanism. This is effected by relative movement of the thread-eyes 53 and 55. As shown in Figs. 1 and 3 during the sewing operation and until the Workclamp is raised the taut thread extends diagonally downwardly through the thread-eyes 53 and 55. When, however, the presser-feet (and therewith the work-clamp) are raised the eye 55 in the arm 3|a is raised relative to and above the stationary eye 53. This snubs the taut thread about the upper wall of the thread-eye 53 and forms a bight b therein, as shown in Figs. 4 and 5, The formation of the bight in the thread requires an additional length of thread which is supplied by the stretching of the thread between the thread-eye 53 and the last stitch anchored in the work, including the loop-retained by the looper. After a substantial portion of the stretch in the thread has been taken out, continued upward movement of the work-clamp causes the limb of the thread-loop which is attached to the work to be broken close to the work, as indicated at ,'f in Figs. 4 and 5, after which the free end e of the thread may be pulled out from the work as for example, by removing the work from the machine.

As shown most clearly in Figs. 3 and 5 the plate 54, in which the thread-eye 53 is formed, is adjustably secured, by screw 80, to the faceplate la. Thus by vertical adjustment of the plate 54 the relation of the thread-eyes 53 and 55 may be varied, whereby the length of the thread forming the bight b may also be varied, thereby to take out more or less stretch in the sewing thread.

From the foregoing it will be apparent that this invention has provided positive yet simple means operative by and during the lifting of the work-clamp rst to take stretch out of a sewing and thereafter to break the thread,- as is common in this type of sewing machine.

carrying needle and a cooperating looper'which thread adjacent the stitch-forming mechanism,

retains a loop of the thread at the end 0f a stitch forming cycle; the improvement which consists in the provision of a stationary threadeye carried by said head and a movable threadeye carried by said presser-bar through which thread-eyes the thread passes in its movement from a source of supply to said stitch-forming mechanism. means to clamp the thread between said source of supply and said thread-eyes, means operable while the thread is clamped and while a thread-loop is retained by said looper to lift said presser-bar and to shift said movable threadeye relative to said stationary thread-eye to form a bight in the thread thereby to stretch said thread and render it comparatively inelastic, and means to lift said work-clamp to strain the f stretched thread to cause breakage thereof.

2. In a cyclically operated sewing machine as set forth in claim 1, in which one of the threadeyes is adjustable with respect to the other thread-eye thereby to vary the amount of stretching action that will be imposed upon the thread by a unit movement of said movable thread-eye.

3. A sewing machine comprising a vertically movable work-clamp, stitch-forming mechanism including a reciprocating needle and a cooperating looper adapted to form stitches in a workpiece held by said work-clamp with a thread having a substantial amount of elasticity, automatically actuated means for clamping the thread before the machine is brought to rest at the completion of a sewing cycle to prevent thread being drawn from the supply, means for lifting said work-clamp at the completion of a sewing cycle and with the last thread-loop held by the looper, thread-snubbing means adjacent the needle and rendered effective by the initial movement of said work-clamp lifting means to snub the thread and simultaneously with said snubbing action to form a bight in that portion of the thread between the thread-snubbing means and the looper to take out of that portion of the thread a substantial portion of its elasticity, whereupon further upward movement of the work-clamp and workpiece carried thereby strains the stretched thread and causes breakage thereof adjacent the workpiece.

4. A cyclically operated sewing machine comprising stitch-forming devices including a needle and a cooperating looper for forming stitches, normally ineifective thread restraining means located between the source of thread supply and said stitch-forming devices, automatically actuated means rendering said thread restraining means effective before the machine is brought to rest to prevent thread from being drawn from the supply, means acting on the thread between said restraining means and said needle to snub the thread and simultaneously therewith to stretch that portion thereof between the snubbing means and the underside of the work, thereby to take out a substantial portion of its elasticity, and means for straining the stretched thread to cause breakage thereof.

5. A sewing machine comprising stitch-forming devices for forming groups of stitches, means for bringing the machine to rest after the com .fpleton -of eelioup of stitches, aa' normally inelective thread-restraining "meens .ffleeatgd @ei-,Ween

--athesource of thread' supplyand said sttchforming devices, means'l aetuatedautomati y y near the completionk of 2f-v. group -of stitchesftelrender 5 i said thread-restraining"meanseffective to prevent fdrawng of thread therethrough, meanwcting on l thee-thread; between saidfrestrainingf meeris-end said stitches, after the machine has been-brought to rest, to stretch that portion of the thread adj acent the stitch-forming idevicesA thereby Ato .take

. .iviIcHAinLl- MccANN. 

